An official announcement on the US-based company that will take over Britain's helicopter search and rescue operations is expected today. The government has awarded the contract to run the service to the Bristow Group, which has its headquarters in Texas.

The announcement – which was previously reported by the Guardian – will bring to an end 70 years of search and rescue operations by the RAF and Royal Navy. It is expected to be made before the stock market opens.

The contract – from 2015 to 2026 – is worth in the region of £3bn. Bristow is said to be planning replace the ageing RAF and Navy Sea King helicopters with faster, more efficient Sikorsky S-92s and AgustaWestland 189s.